1. Field of the Invention
The present invention concerns the use of 4-amino-1,2,4-triazole, as well as hydroxylamine and its O-alkyl derivatives, to provide new and improved syntheses of DATB and TATB by vicarious nucleophilic substitution (VNS) reactions.
2. Description of the Problem and Related Art
Some explosives are more sensitive to shock and heat than others having a similar structure. Studies of explosives based on the benzene ring include, for example, 1,3,5-trinitrobenzene (TNB), 2,4,6-trinitrotoluene (TNT), 1-monoamino-2,4,6-trinitrobenzene (MATB) (aka picramide), 1-3-diamino-2,4,6-trinitrobenzene (DATB) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Although these compounds have much in common, the shock initiation thresholds, that is, the shock pressure required to cause detonation in 50% of the tests, vary widely. Table 1 shows the pattern.
TABLE 1 ______________________________________ SHOCK INITIATION THRESHOLD OF EXPLOSIVES Compound Pressure (kilobars) ______________________________________ TNB 17 TNT 21 MATB 30 DATB 46 TATB 75 ______________________________________
While not wanting to be bound by theory, it appears that adding amino groups to a nitro-substituted benzene ring raises the initiation shock threshold. This pattern occurs, because as the networks of hydrogen bonds increase, the networks absorb energy from a shock front and reduce the amount of shock that goes to the ring itself. See W. Worthy in "Shock Sensitivity of Explosives Clarified", Chemical and Engineering News, p. 25, (Aug. 10, 1987) for further discussion.
It follows that DATB and TATB are highly desirable, insensitive explosives that are used primarily in specialty applications. Part of the reason that they are used in special as opposed to general explosive applications is high cost.
They are too expensive to use in ordinary applications when other less expensive explosives can be used. One reason that TATB is expensive is that it is usually prepared from 1,3,5-trichlorobenzene which is expensive and is not generally available from domestic suppliers. The chloride byproduct (NH.sub.4 Cl) is difficult to remove and may cause compatibility problems in certain types of ordnance (cf. U.S. Pat. No. 4,032,377).
TATB is also valuable in non-explosive applications. K. Praefake and B. Kohne, Ger. Often. DE 3,612,238 disclose the use of TATB to prepare hexaaminobenzene derivatives which are used as components of lyotropic liquid-crystal phases, which can be used in display devices.
Alternative preparations were also sought, and
T. M. Benziger, U.S. Pat. No. 4,032,377 discloses a preparation of TATB by nitration of 1,3,5-trichlorobenzene to 1,3,5-trichloro-2,4,6-trinitrobenzene followed by treatment with ammonia to produce TATB. This patent also discloses the use of water to separate the byproduct ammonium chloride.
D. G. Ott and T. M. Benziger, U.S. Pat. No. 4,952,733 and Journal of Energetic Materials, vol. 5, pp. 343-354 (1987) disclose a preparation of TATB by nitration of 3,5-dichloroanisole to produce 3,5-dichloro-2,4,6-trinitroanisole which is chlorinated to give 1,3,5-trichloro-2,4,6-trinitrobenzene which is ammonolyzed to give TATB.
Additional art of interest includes, for example:
R. T. Atkins et al., in U.S. Pat. No. 4,248,798 disclose a new method for preparing pentanitroaniline (PNA) and triaminotrinitrobenzene (TATB) from TNT. TNT is first reduced using H.sub.2 S to 4-amino-2,6-dinitrotoluene then nitrated using nitric acid/sulfuric acid to pentanitroaniline followed by reaction with ammonia to produce the TATB.
J. Meisenheimer et al., in Chemische Berichte, vol. 39, pp. 2533-2542 (1906) describe the di-amination of 1,3-dinitrobenzene with hydroxylamine under basic conditions to yield 2,4-dinitro-1,3-phenylenediamine.
M. Makosza et al., review and discuss "Vicarious Nucleophilic Substitution of Hydrogen", in Accounts of Chemical Research, vol. 20, pp. 282-9 (1987), and teach the substitution of polynitrobenzene structures with a number of non-nitrogen containing vicarious nucleophilic substitution reagents. No nitrogen-containing reagents are suggested.
A. R. Katritzky and K. S. Laurenzo, Journal of Organic Chemistry, vol. 51, pp. 5039-5040 (1986) disclose mono-amination of nitrobenzene and some substituted nitrobenzenes to give 4-nitroanilines by VNS reactions using 4-amino-1,2,4-triazole. The same authors, in the Journal of Organic Chemistry, vol. 53, pp. 3978-3982 (1988) disclose the use of a series of 4-(alkylamino)-1,2,4-triazoles to transfer the alkylamino group to the 4-position of nitrobenzene and 3-substituted nitrobenzenes by VNS.
J. A. Hoffman and C. F. McDonough, U.S. Pat. No. 3,278,604 and J. C. Dacons et al., in U.S. Pat. No. 3,394,183 both disclose the preparation of DATB via sulfonation and nitration (2 steps) of 1,3-dimethoxy-2,4,6-trinitrobenzene (DMTNB) which is then aminated to give DATB.
T. Urbanski et al., Journal of Scientific and Industrial Research (India), vol. 37, p. 250-5 (1978), disclose the standard preparation and properties of several heat resistant explosives including DATB and TATB.
J. R. Holden et al., U.S. Naval Ordnance Laboratory, White Oak, Md., NAVORD Report 6299 (March 1959), disclose the properties of DATB.
S. K. Yasuda et al., in Journal of Chromatography, vol. 71, p. 484-86 (1972) discuss the separation and identification of 12 impurities of 1,3,5-triamino-2,4,6-trinitrotoluene by two dimensional thin-layer chromatography.
M. Makosza et al., Journal of Organic Chemistry, vol. 57, p. 4784-5 (1992), disclose the mono-amination of nitrobenzenes with sulfenamides via vicarious nucleophilic substitution of hydrogen.
W. P. Norris et al., "CL-14, A New Dense, Insensitive, High Explosive", Naval Weapons Center, China Lake, Calif., Report No. TP 6597 (Unclassified), May 1985, disclose the use of hydroxylamine under basic conditions to di-aminate 4,6-dinitrobenzofuroxan (DNBF) thereby producing 5,7-diamino-4,6-dinitrobenzofuroxan (CL-14).
R. T. Atkins et al., in the Journal of Organic Chemistry, vol. 51, pp. 3261-3266 (1986), disclose the synthesis of a number of polynitro compounds, including TATB. Pentanitroaniline is reacted with ammonia to produce TATB.
J. G. Kaey and E. F. V. Scriven in Chemical Specialties USA 91 Symposium disclose the regiospecific synthesis of 1-substituted-1,2,4-triazoles using 4-amino-1,2,4-triazole.
None of these references individually or collectively teach or suggest the present invention.
It is apparent from this description that there is a need for new processes to easily convert nitroaromatic compounds to DATB, TATB or mixtures thereof. The present invention provides such useful processes which are also environmentally benign.